Solar-driven peroxyacid group activation enables＞ 500 h stable hydroxyl-radical defluorination of industrial perfluorophenol wastewater

Fluoroarenes persist in aquatic environments because aromatic delocalization and aqueous speciation suppress selective C-F bond cleavage, limiting both reductive activation and direct hole oxidation. Hydroxyl radicals (·OH) can mineralize these contaminants, yet near-neutral·OH generation typically relies on added oxidants or Fenton chemistry, creating chemical demand and secondary residues. Here we report a carboxyl-functionalized crystalline perylene diimide photocatalyst (Carboxyl-PDI) that produces ·OH via a catalytic carboxyl-peroxyacid cycle under visible light. Carboxyl-PDI delivers a 50.94% apparent quantum yield for ·OH at 600 nm, achieves complete defluorination of 100 mg L−1 perfluorophenol under AM1.5 G irradiation, and retains stable capacity for >500 h. Isotope labelling mass spectrometry and theoretical calculation identify a -COOOH intermediate and show hydrogen-bond gating to a neighbouring PDI carbonyl weakens the O-O bond by ~0.31 eV, enabling low-barrier homolysis for producing ·OH. A continuous-flow outdoor-sunlight reactor reaches 95.85% degradation, 90.67% defluorination and 79.68% mineralization, demonstrating scalable oxidant-free defluorination of perfluorophenol. A carboxyl-functionalized photocatalyst generates hydroxyl radicals via a catalytic peroxyacid cycle, enabling complete defluorination of industrial-strength perfluorophenol without external oxidants and with >500 h stability under sunlight.